could it be something other than turbo

[duncan502]

Hopefully someone can shed some light on a possible turbo problem. Car is Octavia 2.0 TDi, BKD engine. Yesterday after accelerating coming off a roundabout there was a loss of power, car would not rev past 2500 - 3000 rpm and max speed was about 70 mph.

I have looked on this forum and seems to point to engine going into limp home mode, also this appears to be the case as it seems fine now. Although I haven't yet had a chance to give it some welly and see if it happens again. I have run a diagnostic and the only error code shown was 'engine overboost condition'

I was hoping that someone could suggest a diagnostic route as to possible pipes connections to check before I go down the route of getting a new turbo!!!

Thanks for reading

[martinch]

Hmm ... sounds similar to what happened with my parents - would not rev past 3000rpm in 4th-6th (but would in 3rd), or go above ~70-80mph. It had logged an overboost DTC (if you don't have one, Gendan sell readers - £40 for a basic one, £80 for a whizzo one ). Dealers said that the actuator rod was sticking, and switched the turbo under warranty.

Can't help on the pipework diagnostics :( (I did see someone once say tape the pipes up to rule out leaks, but I'm not sure if removing the tape would lead to damage)

[Dougall]

You've got the same engine as me and to be honest quite a few of us on here have had the turbo go in the last few months.

In theory it could be other things like a pipe with a hole or something but the turbo going on a BKD engine is pretty common. If your car is around 2005/06 and around 85k then more liekly to be the turbo.

With mine it was also logging an overboost when it happend, basically it would go into limp mode which meant I could just reach about 60mph but no power!

The tell tale sign is that when it happens and it goes into limp mode, pull over and turn off and on the ignition. Pull away gently and get the car back up to speed, if the problem has gone or trips back into limp mode after being normal then it's likely to be the turbo.

If it's the turbo, your likely to have a bill of £510 ahead of you for a re-con turbo plus a few hours fitting which is likely to add another £200+

Personally I did think about checking pipes etc first but with the BKD enegine the turbo is behind the block and hard to get at for a nosey. When the garage took my turbo off to have a look, it was pretty knackered and although the probelm was more like sticking vanes the bearings were also shot

[casscat]

Hopefully someone can shed some light on a possible turbo problem. Car is Octavia 2.0 TDi, BKD engine. Yesterday after accelerating coming off a roundabout there was a loss of power, car would not rev past 2500 - 3000 rpm and max speed was about 70 mph.

I have looked on this forum and seems to point to engine going into limp home mode, also this appears to be the case as it seems fine now. Although I haven't yet had a chance to give it some welly and see if it happens again. I have run a diagnostic and the only error code shown was 'engine overboost condition'

I was hoping that someone could suggest a diagnostic route as to possible pipes connections to check before I go down the route of getting a new turbo!!!

Thanks for reading

I've met similar problems in the past with my last car (Octavia TDi), with a dramatic power loss. Both of which cases are not that serious (not as serious as a new turbo!) That said, I didn't check on error codes, if you genuinely have 'overboost' problems then maybe what I'm saying isn't relevant, anyway here goes:

- The most recent case I put down to a contaminated tank of fuel. The problems were just as you describe, a sudden loss of power under acceleration. This started happening not long after I'd refuelled (normal diesel). I definitely used the Diesel pump - I blame the filling station for having dodgy fuel. It was sporadic, you couldn't predict when it was going to lose power (unlike the second scenario I describe below). Anyway I just kept on driving and ran the fuel tank as empty as I dared. Filled up again from a different garage and all was good again, and the problem never came back. At the time though I was scared it was the turbo being about to fail!

- The other time I've met this problem, the root cause was a blocked fuel filter. The difference in the symptoms is that in this case the loss of power was predictable. Initally at high revs (over 3000rpm) if you put your foot down, the car actually slowed down and you could see white smoke coming out of the back. Bit by bit the filter got worse, and the point at which this happened got worse and worse, until eventually doing just 30mph was a challenge. What I haven't said up to know is that with that car, I ran on locally produced commercial biodiesel. I met this problem a couple of times, and started carrying a spare fuel filter with me just in case. Further 'proof' of this problem can be found visually under the bonnet. That Octavia had a clear pipe from the fuel filter to the fuel pump. If you revved the engine, you could see that the pipe was supplying 'foam' rather than liquid diesel because of the blockage in the filter.

If the latter is the case, changing the filter is easy. Basically remove the four pipes from the old one and connect the new one! The only tricky bit is priming the filter. If (as the Haynes manual suggested) you just keep cranking the engine until the pump has filled the new filter with diesel.... then the battery runs flat first. I learned the trick was to fill the new filter with diesel through the hole on top manually, before then installing in the car.

Good luck.

Edited 1 August, 2011 by casscat

[duncan502]

Thanks for the replies and advice I should be able to have a look into it further on Friday.

Although I have since done 30 or 40 miles at motorway speeds and have not experienced the problem again.

So if I could ask further if the engine goes into limp home mode once for overboost from a broken turbo, does it not continualy go into LHM each time the revs reach that point again?

[softscoop]

If it's done it once it could be the start of a sticky VNT mechanism.

Basically soot builts up on the mechanism causing it to stick in a certain position. The turbo will be producing more boost than is requested, so the ECU puts the car in limp mode to protect itself.

Can be sorted DIY although it's a very involved process

[fordfan]

We've had one in recently, checked the VNT mechanism with a vacuum pump and it worked perfectly. We ended up replacing the pressure sensor which is in the pipe that runs below the radiator, two philips screws and an electrical connection. The sensor was less than £60 from VW. Given that this was over two weeks ago and we haven't heard from the customer since, it may have cured it.

The sensor will have a part number on it.